Disclosed are a method and apparatus for determining a pdu session identity in a wireless communication system. A method for determining, by a session management function (SMF) node, a packet data network (pdu) session identity during handover of user equipment (ue) in a wireless communication system, may include receiving a request message for requesting the establishment of a pdu session for the ue from an access and mobility management function (AMF) node, wherein a handover for the ue from a first wireless communication system to a second wireless communication system has been determined, determining a pdu session identity for the pdu session established for the ue when the request message is received, and sending a response message including the determined pdu session identity to the AMF node in response to the request message.
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1. A method for determining, by a session management function (SMF) node, a packet data network (pdu) session identity for one or more pdu sessions of user equipment (ue) in a wireless communication system, the method comprising:
receiving a request message for requesting an establishment of a pdu session for the ue from an access and mobility management function (AMF) node while the ue performs a handover procedure from a first wireless communication system to a second wireless communication system;
determining a pdu session identity for the pdu session established for the ue when the request message is received; and
sending a response message including the determined pdu session identity to the AMF node in response to the request message,
wherein the pdu session identity for the pdu session is determined by combining a specific identity and an identity for locally identifying the pdu session within the SMF node,
wherein the specific identity includes a network slice identity to which the SMF node belongs or a globally unique id allocated to the SMF node.
10. A session management function (SMF) node for determining a packet data network (pdu) session identity for one or more pdu sessions of user equipment (ue) in a wireless communication system, the SMF node comprising:
a communication module configured to send or receive a signal; and
a processor configured to control the communication module, wherein the processor is configured to:
receive a request message for requesting an establishment of a pdu session for the ue from an access and mobility management function (AMF) node while the ue performs a handover procedure from a first wireless communication system to a second wireless communication system,
determine a pdu session identity for the pdu session established for the ue when the request message is received, and
send a response message including the determined pdu session identity to the AMF node in response to the request message,
wherein the pdu session identity for the pdu session is determined by combining a specific identity and an identity for locally identifying the pdu session within the SMF node,
wherein the specific identity includes a network slice identity to which the SMF node belongs or a globally unique id allocated to the SMF node.
2. The method of
a network slice comprising an access network (AN) and a core network (CN) is included in the second wireless communication system,
the AN and the AMF node are common to multiple network slices, and
the SMF node belongs to each network slice.
3. The method of
the network slice identity is allocated by the AMF node, and
the network slice identity is included in the request message and received from the AMF node.
4. The method of
5. The method of
6. The method of
7. The method of
8. The method of
9. The method of
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Pursuant to 35 U.S.C. § 119(e), this application claims the benefit of U.S. Provisional Patent Application Nos. 62/337,349, filed on May 17, 2016, 62/405,265, filed on Oct. 7, 2016, 62/418,801, filed on Nov. 8, 2016, and 62/470,354, filed on Mar. 13, 2017, the contents of which are all hereby incorporated by reference herein in their entirety.
The present invention relates to a wireless communication system, and more specifically, to a method for allocating/determining a packet data network (PDN) session identity and an apparatus supporting the method.
A mobile communication system has been developed to provide a voice service while guaranteeing user mobility. However, the service range of the mobile communication system has been extended to a data service as well as a voice service. Today, a resource shortage phenomenon is generated due to an explosive increase of traffic, and users request higher speed services. Accordingly, a more enhanced mobile communication system is required.
A next-generation mobile communication system should be able to support the acceptance of explosive data traffic, an epochal increase of the transmission rate per user, the acceptance of a large number of increased connection devices, very low end-to-end latency, and higher energy efficiency. For this reason, research is carried out on various technologies, such as dual connectivity, massive multiple input multiple output (MIMO), in-band full duplex, non-orthogonal multiple access (NOMA), super wideband support, and device networking.
In a next-generation wireless communication network, multiple network slices are supported to support different services, and the multiple network slices use a specific network node in common. For this reason, if a PDU session identity is allocated to a PDU session for each different network slice, a problem in that a PDU session identity is duplicated between PDU sessions for the same user equipment (UE) which have been established in several network slices.
An embodiment of the present invention proposes a method for allocating a PDU session identity when a PDU session is established.
Furthermore, an embodiment of the present invention proposes a method for allocating a PDU session identity when a PDU session for a UE is established in a next-generation wireless communication system in order to guarantee service continuity for a PDN connection which is used in a legacy wireless communication system if the UE handovers from a legacy wireless communication system (e.g., an LTE/LTE-A wireless communication system) to a next-generation wireless communication system (e.g., a 5G wireless communication system).
Objects to be solved by the present invention are not limited to the aforementioned objects and those skilled in the art will understand the other objects from the following description.
In an aspect of the present invention, a method for determining, by a session management function (SMF) node, a packet data network (PDU) session identity during handover of user equipment (UE) in a wireless communication system, may include receiving a request message for requesting the establishment of a PDU session for the UE from an access and mobility management function (AMF) node, wherein a handover for the UE from a first wireless communication system to a second wireless communication system has been determined, determining a PDU session identity for the PDU session established for the UE when the request message is received, and sending a response message including the determined PDU session identity to the AMF node in response to the request message.
In an aspect of the present invention, a session management function (SMF) node for determining a packet data network (PDU) session identity during handover of user equipment (UE) in a wireless communication system may include a communication module configured to send or receive a signal and a processor configured to control the communication module. The processor may be configured to receive a request message for requesting the establishment of a PDU session for the UE from an access and mobility management function (AMF) node, wherein a handover for the UE from a first wireless communication system to a second wireless communication system has been determined, determine a PDU session identity for the PDU session established for the UE when the request message is received, and send a response message including the determined PDU session identity to the AMF node in response to the request message.
A network slice including an access network (AN) and a core network (CN) may be included in the second wireless communication system. The AN and the AMF node may be common to multiple network slices. The SMF node may belong to each network slice.
The PDU session identity for the PDU session may be determined by combining a network slice identity to which the SMF node belongs and an identity for locally identifying the PDU session within the SMF node.
The network slice identity may be allocated by the AMF node, and the network slice identity may be included in the request message and received from the AMF node.
If multiple SMFs are present in the network slice, the PDU session identity for the PDU session may be determined by combining an SMF identity for identifying each SMF node within the network slice, a network slice identity to which the SMF node belongs and an identity for locally identifying the PDU session within the SMF node.
The network slice identity and the SMF identity of the SMF node may be allocated by the AMF node and may be included in the request message and received from the AMF node.
The PDU session identity for the PDU session may be allocated by the AMF node and may be determined by receiving the PDU session identity through the request message from the AMF node.
When the PDU session identity is allocated by the AMF node, an association between the PDU session identity and the identity of the SMF node may be generated by the AMF.
When the establishment of the PDU session is rejected, the association between the PDU session identity and the identity of the SMF node may be removed by the AMF.
The PDU session identity for the PDU session may be determined within a PDU session ID pool configured in the SMF node.
The PDU session identity for the PDU session may be determined by combining a globally unique ID allocated to the SMF node and an identity for logically identifying the PDU session within the SMF node.
In accordance with an embodiment of the present invention, each of PDU sessions can be precisely controlled by a network node because a unique identity is allocated to each PDU session.
Furthermore, in accordance with an embodiment of the present invention, in particular, although a UE is connected to several network slices, a specific PDU session-related message can be precisely transmitted or received between a UE and a network slice.
The effects of the present invention are not limited to the aforementioned effects and those skilled in the art will understand the other objects from the following description.
For understanding of the present invention, the accompanying drawings included as part of the detailed description provide embodiments of the present invention and describe the technical characteristics of the present invention together with the detailed description.
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. A detailed description of the present invention to be described hereinafter together with the accompanying drawings describes embodiments of the present invention and does not represent a sole embodiment in which the present invention may be implemented. The following detailed description includes detailed contents in order to provide complete understanding of the present invention. However, a person having ordinary skill in the art may be aware that the present invention may be implemented without such detailed contents.
In several cases, in order to avoid a concept of the present invention from being ambiguous, well-known configurations and devices may be omitted or a core function of each configuration and device may be mainly shown in a block diagram form.
In this specification, a base station (Bs) may be replaced with a term, such as a fixed station, a Node B, an evolved-NodeB (eNB), a base transceiver system (BTS), an access point (AP), a RAN or a 5G-RaN. Furthermore, the term ‘terminal’ may be fixed or may mobile and may be replaced with a term, such as user equipment (UE), a mobile station (MS), a user terminal (UT), a mobile subscriber station (MSS), a subscriber station (SS), an advanced mobile station (AMS), a wireless terminal (WT), a machine-type communication (MTC) device, a machine-to-machine (M2M) device, or a device-to-device (d2d) device.
Hereinafter, downlink (DL) means communication from the BS to the terminal, and uplink (UL) means communication from the terminal t the base station. In downlink, a transmitter may be part of a BS and a receiver may be part of a UE. In uplink, a transmitter may be part of a UE and a receiver may be part of a BS.
Specific terms used in the following description are provided for understanding of the present invention, and use of such a specific term may be changed in other forms without departing from the spirit and scope of the present invention.
Exemplary embodiments of the present invention may be supported by standard documents that describe at least one of IEEE 802, 3GPP, and 3GPP2, which are wireless access systems. That is, in embodiments of the present invention, steps or portions that are not described to clearly expose the spirit and scope of the present invention may be supported by the documents. Furthermore, entire terms of this document may be described by the standard document.
For clear description, 3GPP LTE/LTE-A or 5-generation (5G) system is mainly described, but the technical characteristic of the present invention is not limited thereto.
Terms that may be used in this document are defined as follows.
1) A standalone new radio.
2) A new radio, that is, an anchor supporting the extension of E-UTRA.
3) A standalone E-UTRA.
4) An anchor supporting the extension of a new radio
Embodiments of the present invention are described based on the terms defined as described above.
System to which the Present Invention May be Applied
A network configuration diagram of
The EPC is the core element of system architecture evolution (SAE) for enhancing performance of 3GPP technologies. The SAE corresponds to a research subject to determine a network configuration that supports mobility between various kinds of networks. The SAE has a target that provides an optimized packet-based system that supports various wireless access technologies based on, for example, an IP and that provides a more enhanced data transfer ability.
More specifically, the EPC is the core network of an IP mobile communication system for a 3GPP LTE system and may support a packet-based real-time and non-real-time service. In the existing mobile communication system (i.e., the second-generation or third-generation mobile communication system), the function of the core network was implemented through two different sub-domains of circuit-switched (CS) for voice and packet-switched (PS) for data. However, in the advanced 3GPP LTE system of the third-generation mobile communication system, the sub-domains of CS and PS were unified into a single IP domain. That is, in the 3GPP LTE system, connection between UEs having an IP capability may be formed through an IP-based base station (e.g., an evolved Node B (eNodeB), an EPC, and an application domain (e.g., IMS). That is, the EPC is an essential configuration in implementing an end-to-end IP service.
The EPC may include various elements, and
The SGW operates as the boundary point between a radio access network (RAN) and a core network and is an element that performs the function of maintaining a data path between the eNodeB and the PDN GW. Furthermore, when the UE moves over an area served by the eNodeB, the SGW performs a function of a local mobility anchor point. That is, for mobility within a universal mobile telecommunications system (Evolved-UMTS) terrestrial radio access network defined after 3GPP release-8) (E-UTRAN), packets may be routed through the SGW. Furthermore, the SGW may function as an anchor point for mobility with another 3GPP network (RAN defined prior to the 3GPP release-8, for example, UTRAN or global system for mobile communication (GSM)/enhanced data rates for global evolution (EDGE) radio access network (GERAN)).
The PDN GW corresponds to a termination point of a data interface toward a packet data network. The PDN GW may support policy enforcement features, packet filtering, and charging support. Furthermore, the PDN GW may perform an anchor point function for mobility management with an unreliable network such as a 3GPP network and a non-3GPP network (e.g., an interworking wireless local area network (I-WLAN), a code division multiple access (CDMA) network or a reliable network such as a Wimax).
In the illustration of the network configuration of
The MME is an element that performs the signaling and control functions for supporting access to network connection of the UE, the allocation of a network resource, tracking, paging, roaming and handover. The MME controls control plane functions related to a subscriber and session management. The MME manages many eNodeBs and performs signaling for selection of a conventional gateway for handover of another 2G/3G network. Furthermore, the MME performs a function of security procedures, UE-to-network Session Handling, and idle UE location management.
The SGSN handles the entire packet data, such as user mobility management and authentication of another 3GPP network (e.g., a GPRS network).
The ePDG functions as the security node of an unreliable non-3GPP network (e.g., I-WLAN, WiFi hotspot).
Referring to
Furthermore,
TABLE 1
Reference
point
Description
S1-MME
Reference point for the control plane protocol
between E-UTRAN and MME
S1-U
Reference point between E-UTRAN and Serving GW
for the per bearer user plane tunneling and inter
eNodeB path switching during handover
S3
It enables user and bearer information exchange
for inter 3GPP access network mobility in idle
and/or active state. This reference point may
be used intra-PLMN or inter-PLMN (e.g., in the
case of Inter-PLMN HO).
S4
It provides related control and mobility support
between GPRS Core and the 3GPP Anchor function of
Serving GW. In addition, if Direct Tunnel is not
established, it provides the user plane tunneling.
S5
It provides user plane tunneling and tunnel
management between Serving GW and PDN GW.
It is used for Serving GW relocation due to
the UE mobility and if the Serving GW needs
to connect to a non-collocated PDN GW for the
required PDN connectivity.
S11
Reference point of the control plane protocol
between MME and SGW
SGi
It is the reference point between the PDN GW
and the packet data network. Packet data network
may be an operator external public or private
packet data network or an intra operator packet
data network, e.g. for provision of IMS services.
This reference point corresponds to Gi for 3GPP
accesses.
In the reference points of
The E-UTRAN system is an advanced system of the existing UTRAN system, and may be a 3GPP LTE/LTE-A system, for example. The communication networks are widely disposed to provide various communication services, such as a voice service (e.g., a voice over Internet protocol (VoIP)) through IMS and packet data.
Referring to
An X2 user plane interface (X2-U) is defined between the eNBs. The X2-U interface provides non-guaranteed delivery of a user plane packet data unit (PDU). An X2 control plane interface (X2-CP) is defined between two neighboring eNBs. The X2-CP performs a function of context transfer between the eNBs, the control of a user plane tunnel between a source eNB and a target eNB, transfer of a handover related message, and uplink load management.
The eNB is connected to the UE through a wireless interface and is connected to an evolved packet core (EPC) through an S1 interface.
An S1 user plane interface (S1-U) is defined between the eNB and a serving gateway (S-GW). An S1 control plane interface (S1-MME) is defined between the eNB and a mobility management entity (MME). The S1 interface performs an evolved packet system (EPS) bearer service management function, a non-access stratum (NAS) signaling transport function, network sharing, and a MME load balancing function. The S1 interface supports many-to-many-relation between the eNB and the MME/S-GW.
The MME may perform various functions of NAS signaling security, access stratum (AS) security control, core network (CN) inter-CN signaling for supporting mobility between 3GPP access networks, IDLE mode UE reachability (including the execution and control of paging retransmission), tracking area identity (TAI) management (for idle and active mode UE), PDN GW and SGW selection, MME selection for handover in which the MME is changed, SGSN selection for handover to a 2G or 3G 3GPP access network, roaming, authentication, a bearer management function including dedicated bearer establishment, and public warning system (PWS) (including an earthquake and tsunami warning system (ETWS) and commercial mobile alert system (CMAS)) message transmission support.
Referring to
Referring to
The control plane is a transmitting path of control messages in which the UE and the network use to manage a call. The user plane means a path that transmits data, for example, voice data or Internet packet data generated in an application layer. Hereinafter, each layer of a control plane and a user plane of a wireless protocol will be described.
By using a physical channel, a physical layer (PHY), which is a first layer L1 provides an information transfer service to a superordinate layer. The physical layer is connected to a medium access control (MAC) layer located at a superordinate level through a transport channel, and data are transmitted between the MAC layer and the physical layer through the transport channel. The transport channels are classified according to a method and feature in which data are transmitted through a wireless interface. Data is transmitted between different physical layers and between the physical layer of a transmitting UE and the physical layer of a receiving UE through the physical channel. The physical layer is modulated with an orthogonal frequency division multiplexing (OFDM) method and uses a time and a frequency as a radio resource.
Several physical control channels are used in the physical layer. A physical downlink control channel (PDCCH) notifies UE of the resource allocation of a paging channel (PCH) and downlink shared channel (DL-SCH) and hybrid automatic repeat request (HARQ) information related to an uplink shared channel (UL-SCH). Furthermore, the PDCCH may transmit an UL grant that notifies UE of the resource allocation of uplink transmission to the UE. A physical control format indicator channel (PDFICH) notifies UE of the number of OFDM symbols used for PDCCHs and is transmitted for each subframe. A physical HARQ indicator channel (PHICH) transmits a HARQ acknowledge (ACK)/non-acknowledge (NACK) signal in response to uplink transmission. A physical uplink control channel (PUCCH) transmits uplink control information, such as HARQ ACK/NACK, a scheduling request, and a channel quality indicator (CQI) for downlink transmission. A physical uplink shared channel (PUSCH) transmits an UL-SCH.
The MAC layer of the second layer L2 provides a service to a radio link control (RLC) layer, which is a superordinate layer through a logical channel. Furthermore, the MAC layer includes a mapping function between the logical channel and the transport channel and a multiplexing/demultiplexing function to a transport block provided to a physical channel on a transport channel of a MAC service data unit (SDU) that belongs to the logical channel. The RLC layer of the second layer L2 supports reliable data transmission. A function of the RLC layer includes concatenation, segmentation, and reassembly of an RLC SDU. In order to guarantee various quality of services (QoS) in which a radio bearer (RB) requires, the RLC layer provides three operation modes of a transparent mode (TM), an unacknowledged mode (UM), and an acknowledge mode (AM). An AM RLC provides error correction through an automatic repeat request (ARQ). When the MAC layer performs an RLC function, the RLC layer may be included as a function block of an MAC layer.
The packet data convergence protocol (PDCP) layer of the second layer L2 performs a transfer function of user data in a user plane and a header compression and ciphering function. In order to efficiently transmit an Internet protocol (IP) packet such as Internet protocol version 4 (IPv4) or Internet protocol version 6 (IPv6) through a wireless interface having a small bandwidth, a header compression function means a function of reducing an IP packet header size having a relatively large size and that contains unnecessary control information. A function of a PDCP layer in the control plane includes transfer of control plane data and ciphering/integrity protection.
A radio resource control (RRC) layer located at the lowermost portion of a third layer L3 is defined in only the control plane. The RRC layer performs the function of controlling a radio resource between the UE and the network. For this reason, UE and the network exchange an RRC message through the RRC layer. The RRC layer controls a logical channel, a transport channel, and a physical channel in relation to a configuration, a re-configuration, and release of radio bearers. For data transmission between UE and a network, the radio bearer means a logical path provided by the second layer L2. A configuration of a radio bearer means prescription of a feature of a wireless protocol layer and a channel in order to provide a specific service and a configuration of each detailed parameter and operation method. The radio bearer may be again divided into two of signaling RB (SRB) and data RB (DRB). The SRB is used as a path that transmits an RRC message at the control plane, and the DRB is used as a path that transmits user data at the user plane.
A non-access stratum (NAS) layer located as the superordinate layer of the RRC layer performs a function of session management and mobility management.
One cell forming a BS is set to one of bandwidths such as 1.25, 2.5, 5, 10, and 20 MHz to provide a downlink or uplink transmission service to several UEs. Different cells may be set to provide different bandwidths.
A downlink transport channel that transmits data from the network to the UE includes a broadcast channel (BCH) that transmits system information, a PCH that transmits a paging message, and a DL-SCH that transmits user traffic or a control message. Traffic or a control message of downlink multicast or a broadcasting service may be transmitted through the DL-SCH or through a separate downlink multicast channel (MCH). An uplink transport channel that transmits data from the UE to the network includes a random access channel (RACH) that transmits an initial control message and an uplink shared channel (UL-SCH) that transmits user traffic or a control message.
The logical channel is the superordinate channel of the transport channel and is mapped to the transport channel. The logical channel may be divided into a control channel for transfer of control area information and a traffic channel for transfer of user area information. The control channel includes a broadcast control channel (BCCH), a paging control channel (PCCH), a common control channel (CCCH), a dedicated control channel (DCCH), and a multicast control channel (MCCH). The traffic channel includes a dedicated traffic channel (DTCH) and a multicast traffic channel (MTCH). The PCCH is a downlink channel that transfers paging information and is used when a network does not know a cell to which the UE belongs. The CCCH is used by the UE that does not have RRC connection to the network. The MCCH is a point-to-multipoint downlink channel used for transferring Multimedia Broadcast and Multicast Service (MBMS) control information from the network to UE. The DCCH is a point-to-point bi-directional channel used by UE having RRC connection that transfers dedicated control information between the UE and the network. The DTCH is a point-to-point channel used for only one UE in order to transfer user information that may exist at an uplink and a downlink. The MTCH is a point-to-multipoint downlink channel in order to transfer traffic data from the network to the UE.
In uplink connection between the logical channel and the transport channel, the DCCH may be mapped to the UL-SCH, the DTCH may be mapped to the UL-SCH, and the CCCH may be mapped to the UL-SCH. In downlink connection between the logical channel and the transport channel, the BCCH may be mapped to the BCH or the DL-SCH, the PCCH may be mapped to the PCH, the DCCH may be mapped to the DL-SCH, the DTCH may be mapped to the DL-SCH, the MCCH may be mapped to the MCH, and the MTCH may be mapped to the MCH.
Referring to
One subframe having a length 1.0 ms is configured with a plurality of symbols. Specific symbol(s) (e.g., a first symbol of the subframe) of the subframe may be used for a PDCCH. The PDCCH transmits information (e.g., resource block) about a dynamically allocated resource and a Modulation and Coding Scheme (MCS).
Method of Identifying PDU Session
Today, in 3GPP, a network configuration, such as that of
Referring to
The network slice may mean a logical network including a set of network functions (NFs) and corresponding resources necessary to provide a specific network capability and network characteristics. That is, the network slice may include both a 5G-AN and a 5G CN. A network slice instance (NSI) or a network instance is an instantiation of a network slice. That is, the NSI may mean a set of deployed NFs that provide an intended network slice service according to a network slice template.
Furthermore, the slices may use some network functions (NFs) in common.
As illustrated in
In LTE/LTE-A networks, mobility and session management have been managed by one node called the MME. In the 5G network, however, such mobility and session management are divided into a mobility management (MM) function and a session management (SM) function and discussed.
The common CNI may include the function of managing the mobility of UE (i.e., an MM function (MMF) or an access and mobility management function (AMF)). The non-common CNI may include the function of managing the session of UE (i.e., an SM function (SMF)).
The MMF (or AMF) may also be called a common control plane function (C-CPF).
Furthermore, the common CNI may include a network slice selection function (NSSF) and/or a control plane selection function (CPSF). In other words, the MMF (or AMF or C-CPF) may include the NSSF and/or the CPSF.
Furthermore, the common CNI may be simply called an MMF (or AMF or C-CPF).
Furthermore, the common CNI may also be called a common control plane (CP), and the non-common CNI may be simply called a CNI.
The non-common CNI may include a non-common control plane (CP) function and a non-common user plane (UP) function.
In the architecture of
In the network configuration, such as
In this case, an NSSF and a CPSF within the common CNI may check/determine that the session request message has to be transferred to which network slice.
Thereafter, when an SMF within a non-common CNI generates a session and sends a response message in response to the session request message to an MMF within the common CNI, the MMF may transfer the response message to the UE.
One UE may be served by one or more network slice instances (i.e., non-common CNIs) at the same time over a 5G-AN (the RAN in
An MMF (or AMF) that provides the service to the UE may belong to each network slice instance (i.e., a non-common CNI) that serves the UE. That is, the MMF (or AMF) instance may be in common to network slice instances (i.e., non-common CNIs) that serve the UE.
A PDU session may belong to a specific network slice instance (i.e., non-common CNI). Although different network slices have a slice-specific PDU session using the same data network name (DNN), the different network slices instance (i.e., non-common CNI) may not share the PDU session.
An SMF selection function (e.g., CPSF) may be supported by the MMF (or AMF). The SMF selection function (e.g., CPSF) may be used to allocate an SMF that manages the PDU session.
According to a conventional method, since the SMF manages a PDU session, a PDU session identity is allocated by the SMF, and it is used by UE and other network functions for session management (e.g., session modification and session termination).
If UE is served by a single network slice, an MMF (or AMF) within a common CNI may transfer a session-related message to a corresponding network slice without additional information because a network slice to which a session-related message has to be transmitted has always been determined.
However, in accordance with an existing method, if UE has been connected to several network slices (i.e., non-common CNIs), session IDs allocated by an SMF may be duplicated because an SMF within each of different network slices allocates a session ID (or session identity). In this case, there may be a problem in that an MMF (or AMF) is unaware that a session-related message has to be transferred to which network slice (i.e., which non-common CNI).
Embodiments of the present invention propose methods for solving the problem.
Option 1. A method Using a Different PDU Session ID Pool for Each Non-Common CNI
Option 1 is to use a different PDU session identity pool in each core network instance (i.e., non-common CNI). This mechanism is similar to an IP address pool in each P-GW. For example, a core network instance #1 has a PDU session identity pool from 1 to 100 and a core network instance #2 has a PDU session identity pool from 101 to 200.
That is, a PDU session ID pool may be preconfigured in an SMF within a non-common CNI by an operator.
In this case, the range of a PDU session ID allocated in each SMF may be determined within the pool only.
That is, when the SMF receives a session request message from UE via an MMF (or AMF), it may generate a PDU session and allocate a PDU session ID to a corresponding PDU session. When the PDU session ID is allocated, the SMF may select the PDU session ID randomly or using a specific rule within a preconfigured PDU session identity pool. Furthermore, when the SMF sends a session response message to the UE via MMF (or AMF) as a response to the session request message, it may include the session response message in the allocated PDU session ID and send the session response message.
As described above, a PDU session ID is determined within a set PDU session identity pool for each SMF. Although several SMFs individually allocate PDU session IDs to sessions, only an always unique value according to a corresponding session may be configured in UE and an MMF (or AMF).
This mechanism is simple, but an operator should configure each PDU session identity pool both in a common CP (i.e., common CNI) and a core network instance (i.e., non-common CNI). As a result, flexibility is low and the scale-in/scale-out capability may be limited because a maximum number of PDU sessions are limited by the capacity of the PDU session identity pool.
Option 2. A Method of Allocating a Network Slice ID
Option 2 is to use a network slice identity and to provide it to UE during a session establishment procedure. An operator configuration is not needed, but each session management message should contain a network slice identity. Then, the UE recognizes a network slice, which may be undesirable by an operator who does not want to expose a network configuration.
Referring to
When the MMF (or it may be a separate independent function) within a common CNI generates a session and selects a network slice (i.e., non-common CNI), it may notify the UE and an SMF of a network slice identity.
The MMF (or AMF) may allocate a network slice identity to a selected network slice (i.e., non-common CNI) (S702).
Alternatively, when the MMF (or AMF) receives a session response message from the SMF, it may allocate the network slice identity to the selected network slice (i.e., non-common CNI). That is, step S702 may be performed after step S704.
Furthermore, the MMF (or AMF) may transfer the session request message to the SMF within the selected network slice (i.e., non-common CNI) (S703).
The SMF may allocate a PDU session ID to a corresponding session and send a session response message as a response to the session request (S704).
The MMF (or AMF) may include the allocated network slice identity in the session response message, received from the SMF, and send the session response message to the UE (S705).
Accordingly, the UE may be aware of information about the network slice (i.e., non-common CNI) allocated thereto.
The UE may send the allocated network slice identity and PDU session ID through a session-related message whenever it sends the session-related message. In this case, the MMF may determine that the corresponding session-related message has to be transmitted to which network slice using the network slice identity included in the session-related message.
Alternatively, the MMF (or AMF) may transfer the network slice identity to the SMF (S703). Furthermore, when the SMF generates the PDU session ID, it may generate the PDU session ID by including network slice identity in the PDU session ID. In this case, the MMF (or AMF) may not directly transfer the network slice identity to the UE unlike in
Furthermore, the MMF (or AMF) may directly send the network slice identity to the SMF (S703). The SMF may include the network slice identity in the session response message and send the session response message to the MMF. Even in this case, the MMF (or AMF) may not directly transfer the network slice identity to the UE unlike in
Option 3. A method of Allocating, by a Common CNI (MMF/AMF) a PDU Session Identity (ID)
Option 3 is to assign a PDU session identity in common CPs (i.e., common CNIs (MMF/AMF)). An SMF manages PDU sessions, but the PDU session identity is allocated by the common CPs (i.e., common CNIs (MMF/AMF)) so that the PDU session identity is not duplicated. However, this option does not comply with network slicing architecture in which all of SM-related functions are located in a core network instance (i.e., a non-common CNI).
Referring to
When the MMF (or it may be a separate independent function) within a common CNI receives the session request message from the UE, it may directly allocate a PDU session ID (S802).
In this case, if the MMF (or AMF) has information about all of network slices to which the UE is connected and directly allocates the PDU session ID, unique values may be allocated without the duplication of PDU session IDs.
In a conventional technology, a PDU session ID has been determined by an SMF, but such a technology may be called a method for being performed only a portion among the operation of the SMF that the PDU session ID is allocated by a common CNI. That is, in the conventional technology, the SMF directly manages a session. In this method, however, an interaction between two nodes is required because some functions of the SMF have moved to the MMF.
The MMF (or AMF) sends the allocated PDU session ID to an SMF along with the session request message (S803).
The SMF stores and uses the PDU session ID allocated by the MMF (or AMF) (S804).
In this case, when the MMF directly transfers the session request message as in
The SMF includes the PDU session ID, allocated by the MMF, in a session response message and sends the session response message to the MMF (S805).
In this case, when the MMF allocates the PDU session ID, it may allocate the PDU session ID so that it has dependency on each network slice. For example, Nos. 1˜10 PDU session IDs may be allocated to a network slice 1, and Nos. 2˜10 PDU session IDs may be allocated to a network slice 2.
In this case, only the PDU session ID is transferred to the UE, but the MMF has allocated the PDU session ID to the UE so that the PDU session ID has dependency on each network slice depending on the policy of the MMF. Accordingly, the UE may check even information about a network slice that manages a corresponding session.
In the situation in which the MMF allocates the PDU session ID as described above, the SMF may reject the generation of the PDU session requested by the UE. In this case, the MMF needs to perform an operation for removing the previously allocated PDU session ID.
To this end, the MMF has to check SM messages (i.e., the session request message, the session response message and the session reject message) exchanged between the UE and the SMF. If the generation of the PDU session is rejected as a result of the check, the MMF has to perform an operation for deallocating/removing the PDU session ID. This is described below with reference to
Referring to
When the MMF (or it may be a separate independent function) within a common CNI receives the session request message from the UE, it may directly allocate a PDU session identity (S902).
The MMF (or AMF) sends the allocated PDU session ID to an SMF along with the session request message (S903).
If the session requested by the UE is accepted by a network, the SMF sends a session accept message (e.g., a create PDU session accept message) to the MMF (or AMF) as a response to the session request message (S904).
The MMF (or AMF) sends the session accept message to the UE (S905).
In contrast, if the session requested by the UE is rejected by the network, the SMF sends a session reject message (e.g., a create PDU session reject message) to the MMF (or AMF) as a response to the session request message (S906).
When the MMF (or AMF) receives the session reject message from the SMF, it deallocates the PDU session ID allocated to a corresponding session (i.e., the session whose creation was requested by the UE) at step S902 (S907).
Furthermore, the MMF (or AMF) sends a session reject message to the UE (S908).
Furthermore, in addition to the example of
If the PDU session is implicitly released without signaling between the UE and the SMF, there is a problem in that it is difficult for the MMF (or AMF) to be aware of such implicit release. In order to solve such a problem, a method of recognizing, by the MMF (or AMF), that a PDU session has been implicitly released using a timer may be applied, but such a method has low accuracy.
As a result, the MMF (or AMF) has to always monitor SM messages between the UE and the SMF as described above. In order to solve such a problem, the MMF (or AMF) may allocate a PDU session ID only when the SMF requests an allocation of the PDU session ID. This is described below with reference to
Referring to
When the MMF (or it may be a separate independent function) within a common CNI receives the session request message from the UE, it transfers the session request message to an SMF (S1002).
If the session requested by the UE is accepted by a network, the SMF sends a PDU session ID allocation request message to the MMF (or AMF) in order to request the allocation of a PDU session ID (S1003).
When the MMF (or AMF) receives the PDU session ID allocation request from the SMF, it may directly allocate a PDU session identity (S1004).
Furthermore, the MMF (or AMF) sends a PDU session ID allocation response message, including the allocated PDU session identity, to the SMF (S1005).
The SMF sends a session accept message (e.g., a create PDU session accept message) to the MMF (or AMF) as a response to the session request message (S1006).
The MMF (or AMF) transfers the session accept message to the UE (S1007).
In contrast, if the session requested by the UE is rejected by the network, the SMF sends a session reject message (e.g., a create PDU session reject message) to the MMF (or AMF) as a response to the session request message (S1008).
When the MMF (or AMF) receives the session reject message from the SMF, it transfers the session reject message to the UE (S1009).
That is, in accordance with the method of
Although not illustrated in
As a result, in accordance with such a method, the MMF does not need to always monitor SM messages between the UE and the SMF, but there is a disadvantage in that signaling for exchanging PDU session ID allocation/deallocation request messages between the MMF and the SMF is increased.
Option 4. A Method Using a Globally Unique SMF Identity (ID)
If each SMF has a globally unique ID, when the SMF allocates a PDU session ID, it may include its own unique ID in the PDU session ID and allocate the PDU session ID.
If such a method is used, a load for signaling may be increased because the size of the PDU session ID may be excessively increased.
The reason why a unique SMF ID is not used within a PLMN is that if UE uses PDU sessions of a local breakout method and a home-routed method at the same time when performing roaming, an SMF having a session established with one UE may be located in a different PLMN. Accordingly, there is a problem in that a roaming scenario is not supported if a unique SMF ID is used within a PLMN.
If several SMFs are present within a single non-common CNI, the method of Option 1, Option 3 and Option 4 may be applied. In the case of Option 1, a different pool may be set for each SMF. In the case of Option 3, several SMFs may identically operate although they are located within a single slice because an MMF allocates a PDU session ID.
In contrast, in the case of Option 2, a PDU session is identified based on a combination of a network slice identity and a session ID. Accordingly, if several SMFs are present within a single network slice, there is a problem in that sessions cannot be clearly distinguished. In order to solve such a problem, an MMF within a common CNI may allocate a network slice identity, may also allocate an ID by which an SMF within a non-common CNI can be uniquely identified, and may transfer the network slice identify and the ID to an SMF and UE. In this case, a unique PDU session ID can be allocated while maintaining the PDU session ID to a small size compared to Option 4.
Table 2 illustrates advantages and disadvantages of the methods according to the options.
TABLE 2
Advantages
Disadvantages
Option 1
A simple method because
Low flexibility because an
each SMF allocates a
operator has to preconfigured
session ID within a pool
an ID pool within each SMF
Option 2
High flexibility because
A complicated allocation
a PDU session ID can be
process because a PDU
dynamically allocated.
session ID includes a
The size of a PDU session
combination of several IDs.
ID can be reduced because
a global ID is not used.
Option 3
No need for a pool
An MMF and an SMF are not
configuration and a simple
fully separated because an
session ID allocation
MMF performs an operation
method because an MMF
that must be performed by
allocates a session ID.
an SMF.
This option cannot be used
if an MMF managing 3GPP
access and an MMF managing
non-3GPP access are separated.
(in order to use this option,
a PDU session needs to be
separately stored and managed
for each access.
Option 4
A simple method because
Flexibility may be low and the
each SMF allocates a
size of a PDU session ID may
session ID.
be excessively increased
because an operator has to
perform setting so that each
SMF has a globally unique
session ID.
To enable UE to simultaneously obtain services from multiple network slices of one network operator, the core network instances may be set up as depicted in
That is:
common C-plane functions to multiple core network instances may be:
Dedicated C-plane functions for each core network instances may be:
As a deployment option all the C-plane functions may be deployed as part of a common C-plane function as described in
The direct CP interface between RAN and CP-functions of CN instance is not needed, since the encrypted NAS signaling message has to be decrypted by a common C-Plane function, which has exchanged the encrypted key with UE, for example, the AU function.
In case of UE accessing a single a core network instance, RAN may have a direct CP interface to the specific CP function located within a core network instance. In such case, those CP functions depicted as a part of common CP function are considered to be CP functions resided within a core network instance, and hence, there is no common CP function.
The principles of the solution depicted in
The CCPSF is not a function to route the NAS signaling message to the right common C-plane function. In this solution, it is assumed that the RAN has a function to route the NAS signaling message to a proper common C-plane function by taking the information that is sent by the CCPSF in case of the first initial connection request or by UE in case of any subsequent NAS messages.
When UE establishes a PDU session, the PDU session is identified as follows:
Option A: Each core network instance has instance identity which uniquely identifies a core network instance. This identity is transferred to UE and the UE includes a core network instance identity in each session management message. The PDU session is identified by combining a core network instance Identity and the PDU session identity assigned by SMF.
Option B: C-plane functions that are common to multiple core network instances allocates PDU session identity when UE requests new PDU session. The PDU session identity is transferred to the SMF.
Option C: Operator configures different PDU session identity pool in each core network instance.
Option D: UE assigns the PDU session identity and it is sent to the network during the PDU session establishment procedure.
In this solution, the “UE usage type”, “DCN-ID”, “service type” and “DNN” are used for the purposes as described below:
Taking the above explanation into account, selecting a proper CNI for the service type that is requested by the UE may be done by using the DNN parameter.
In
Furthermore, the common CP-function may be called an AMF. In this case, the CCPSF and/or NSSF may be supported by the AMF. Furthermore, the AU (or AUSF) may be configured as a node different from the common CP-function (or AMF).
Taking the above explanation into account, selecting a proper CNI for the service type that is requested by the UE may be done by using the DNN parameter.
1. When UE first connects to an operator's network or registers to the PLMN for the first time and there is no sufficient information for the RAN to route this network connection request to an appropriate common C-plane function, the UE sends a network connection request to the RAN, which is then further forwarded to the default common C-plane function. The flow continues in step 2.
If the UE provides the DCN-ID along with this network connection request, but does not provide a temporary UE identity, the RAN uses this DCN-ID to determine an appropriate Common CP that supports this DCN-ID, and the flow continues in step 4. In addition, the UE may provide other information, e.g., service type and/or DNN along with this network connection request.
If the UE provides the temporary UE identity, the RAN uses the temporary UE identity to determine a common CP function specific for CNI-1 and CNI-2 and, the flow continues in step 4. In addition, the UE may provide other information, e.g., DCN-ID, service type and/or DNN along with this network connection request.
When the UE sends a request to connect to an operator's network, UE may request to establish a session for a particular service by sending the DNN along with this network connection request. If this is the case, after the authentication and authorization in step 6 has been performed, the C-CPF specific for CNI-1 and CNI-2 will establish the session for the request service like similar to step 9, 10 and 11.
2. The CCPSF located in the default C-CPF determines which Common C-Plane function to be connected to by taking into account information in the network connection request from UE in step #1. In addition, other information from the subscription database may be also considered. For example, the UE's subscription may indicate that for this UE, the operator should set up a session with the particular CNI. In this signaling flow example depicted in
If a default C-CPF determines that it will serve this UE's network connection request, it either continues with the authentication and admitting the UE to attach/connect to operator's network or reject this UE's network connection request and hence this procedure ends in this step. It is to note that this specific case is not depicted in
3. The default C-CPF sends a response to the RAN node with the Common C-Plane function specific for CNI-1 and CNI-2, for which the UE to attach. Same content of UE's network connection request in step #1 and may also include e.g., DCN-ID from step #2 is also sent back to the RAN.
4. If the UE provides a temporary UE identity, this means that the UE has been once registered at the PLMN, and the CN has provided the UE the DCN-ID, which the UE should be connected. Hence, the RAN uses only the temporary UE identity to route the NAS message to the appropriate common CP function.
In case there is a pool of common C-plane functions that are dedicated for this UE usage type and/or for this DCN-ID provided by the UE or by the default common C-plane function in step #3, the RAN node performs NAS Node Selection Function (NNSF) similar to what we have for the NNSF in eNB.
5. The RAN node routes the UE's network connection request to the common C-plane function specific for CNI-1 and CNI-2. Along with this request, it may contain other information like the DNN to enable the C-CPF specific for CNI-1 and CNI-2 to select a CNI that is specific for a certain service type. If the C-CPF specific for CNI-1 and CNI-2 rejects the UE's network connection request, the C-CPF specific for CNI-1 and CNI-2 sends a NAS reject message to the UE.
6. Authentication and admitting the UE to attach/connect to operator's network is performed.
In this step, the key for decrypting NAS message between the UE and the common CP function specific for CNI-1 and CNI-2 is also provided.
7. The common CP function specific for CNI-1 and CNI-2 sends a network connection accept response to the UE. In this response, it contains the temporary UE identity and the information, for which the UE is to be configured, e.g., which DCN-ID, its corresponding service type and/or corresponding DNN that the UE is allowed to connect. In case, the DCN-ID newly provided does not match to the ones that the UE already has, the DCN-ID(s) will be configured at the UE.
8. UE requests for establishment of a session for a communication service (e.g., service #1 that is provided by a core network instance #1) by sending an SM request for a new PDU session. In this the PDU session request, the UE provides the DCN-ID and DNN.
9. The RAN forwards the PDU session request to an appropriate Common C-Plane function specific for CNI-1 and CNI-2 by using the DCN-ID information sent by the UE.
10. The NSSF in the C-CPF specific for CNI-1 and CNI-2 selects the C-plane function of a core network instance #1 by using the DNN information that may be mapped to represent the service type that the CNI supports in the PDU session request, and forwards the UE's the PDU session request for the service #1 to the CPF-1 in a core network instance #1 (CNI-1 CPF-1), which is responsible for session management in CNI#1. Note that this forwarded the PDU session request still contains the information that has been sent by the UE such as the UE usage type, DCN-ID and DNN.
11. The CPF-1 in a core network instance #1 sends the session setup message to the UPF-1 in a core network instance #1 for session establishment. After a successful session establishment, the CPF-1 in a core network instance #1 sends the session response back to the C-CPF specific for CNI-1 and CNI-2.
12. The C-CPF specific for CNI-1 and CNI-2 sends a new service response back to the UE via RAN. After this step, the UE is successfully connected to a core network instance #1 with an active the PDU session.
13. The UE requests the establishment of another session for a new communication service that is of a different service type than the previous service. In the PDU session request, the UE provides the temporary UE identity, UE usage type, DCN-ID, and service type and/or DNN.
14. The RAN determines the common C-plane function specific for CNI-1 and CNI-2 by using the temporary UE identity sent by the UE and forwards the PDU session request to the common C-plane function specific for CNI-1 and CNI-2.
15. The C-CPF specific for CNI-1 and CNI-2 selects C-plane function of a core network instance #2 by using the DNN information in the PDU session request, and forwards the UE's service request for the new service to the CPF-1 in a core network instance #2 (i.e., CNI-2 CPF-1), which is responsible for session management in CNI #2. Note that this forwarded the PDU session request still contains the information that has been sent by the UE such as the UE usage type, DCN-ID, and service type and/or DNN.
16. The CPF-1 in the core network instance #2 sends the session setup message to the UPF-1 in the core network instance #2 for session establishment. After a successful session establishment, the CPF-1 in the core network instance #2 sends the session response back to the C-CPF specific for CNI-1 and CNI-2.
17. The C-CPF specific for CNI-1 and CNI-2 sends a new service response back to the UE via RAN. After this step, the UE is successfully connected to a core network instance #2 with an active the PDU session.
As described above, there are four options (i.e., option A to D) to assign the PDU session identity.
Those options A to D may be separated by two methods. One method is a UE-based solution and the other is a network-based solution.
In the EPS, a default bearer id is used to identify a PDN connection and it is assigned by a network, i.e., the MME.
If UE allocates a PDU session ID, a network needs to validate the ID because there is a possibility of mis-configuration or malfunctioning.
But the SMF doesn't have enough information to validate the UE provided identity because the SMF doesn't have other the PDU session information assigned by another SMF. The SMF needs to exchange signaling with the MMF to validate the PDU session information. The signaling should be performed whenever new PDU session is established. So it is proposed to assign the PDU session ID by the network
Therefore, the present invention proposes that a network allocates a PDU session identity.
There are three network-based solutions (i.e., options A to C).
In option B, common CP functions (i.e., the common CNI) may allocate the PDU session identity. The possible common CP function may be an MMF (or AMF). So this option may be not aligned with network slicing architecture which all of SM-related functions are located in a core network instance (i.e., non-common CNI). If two different MMFs are required when UE simultaneously attached using 3GPP access and non-3GPP access, this option is not a feasible option.
In option C may be using different PDU session identity pool in each network slice Instance (NSI). This mechanism is similar to IP address pool in each P-GW. This mechanism is simple but operator should configure each PDU session identity pool both in Common CP and NSI.
As a result, flexibility is low and may limit scale-in/scale-out capability because the number of maximum the PDU session is limited by capacity of PDU session identity pool. When UE is roaming and has two different PDU sessions, i.e., one for home-routed roaming and the other for local breakout, this option cannot be used because operator configured pool is unique in its PLMN.
In option A, a PDU session may be identified by a combination of an NSI identity and a PDU session identity which is locally assigned by an SMF. During the PDU session establishment procedure, NSI identity is transferred to the UE and the UE includes NSI identity in the session management message. The NSI identity is also used by the MMF to route SM messages. In this option, it is assumed that there is one SMF in each NSI. If there are multiple SMFs in an NSI, the MMF needs to allocate SMF identity unique in the NSI.
Therefore, the PDU session may be identified by combination of NSI identity and the PDU session identity locally assigned by the SMF. In case there are multiple SMFs in an NSI, the MMF needs to allocate the SMF identity unique in the NSI. The PDU session is identified by combination of NSI identity, the SMF identity assigned by the MMF and the PDU session identity.
When the UE establishes the PDU session, the PDU session is identified as follows:
Each core network instance has instance identity which uniquely identifies a core network instance. This identity is assigned by the MMF (or AMF) and transferred to the UE. The UE includes a core network instance Identity in each session management message. The PDU session is identified by combining a core network instance identity and a PDU session identity assigned by the SMF.
If there are multiple SMFs in a core network instance, the MMF allocates the SMF identity unique in a core network instance. In this case, a PDU session is identified by a combination of a core network instance identity, an SMF identity allocated by the MMF, and a PDU session identity allocated by the SMF.
Network slicing is described in brief as follows based on the contents of the above description.
An interaction between the MM and the SM may be performed as follows.
UE having multiple established PDU sessions may be served by different instances of an SMF. An MMF selects SMF for PDU sessions. The MMF may select different SMF for different PDU sessions.
However, how the MMF selects the SMF has not been defined.
Accordingly, an embodiment of the present invention proposes an operation of selecting, by the MMF, the SMF based on session-related information (e.g., a DNN) provided by UE in order to clearly define an interaction between the MMF and the SMF. That is, the MMF may use the session-related information (e.g., DNN) provided by the UE.
Furthermore, in relation to PDU session identification, today, in accordance with the solution (i.e., an interaction between MM and SM) of 3GPP TR 23.799 Paragraph 6.4.16, a PDU session identity may be allocated by an MMF. The solution of Paragraph 6.4.16 is as follows.
The PDU session identity is allocated by the MMF: when it starts a new PDU session, the UE uses a default dummy the PDU session identity and upon reception of the corresponding SM signaling, the MMF allocates the PDU session identity for that the PDU session
However, the solution of Paragraph 6.4.16 has not clearly defined that the MMF allocates a PDU session identity when and how.
Accordingly, an embodiment of the present invention proposes two methods of allocating, by the MMF, a PDU session identity.
First, the first method is described below with reference to
The MMF allocates the PDU session identity at step 902 when the MMF receives create PDU session request message from the UE at step 901.
Then the MMF forwards the received create PDU session request message with a newly allocated the PDU session identity to the SMF at step 903. The MMF makes an association between the SMF ID and the PDU session identity.
When the SMF receives the request message and accepts to establish the PDU session, the SMF sends create PDU session accept message to the MMF with the PDU session identity at step S904.
Then, the MMF forwards the received create PDU session accept message to the UE at step S905.
However, if the SMF rejects to establish the PDU session, the allocated the PDU session identity should be deallocated by the MMF and the association between the SMF Id and the PDU session identity should be removed.
Thus, if the SMF rejects to establish the PDU session, the SMF sends create PDU session reject message to the MMF at step 906.
When the MMF receives create PDU session reject message from the SMF, the MMF deallocates the allocated the PDU session identity and removes the association between the SMF Id and the PDU session identity at step 907.
Then, the MMF forwards the received create PDU session reject message to the UE at step S908.
This method assumes that the MMF recognize the exact type of the SM message, i.e., whether the SM message is create PDU session request message or create the PDU session accept/reject message.
Next, the second method is described below with reference to
The second method is to allocate a PDU session identity when the MMF receives an explicit request from the SMF.
The MMF transparently relays a create PDU session request message to the SMF at step 1002 when the MMF receives the create PDU session request message from the UE at step 1001.
If the SMF accepts the request, the SMF requests the allocation of the PDU session identity from the MMF at step 1003. That is, the SMF sends a PDU session ID allocation request message to the MMF.
The MMF allocates the PDU session identity and makes an association between the SMF ID and the PDU session identity at step 1004.
The MMF sends the PDU session ID allocation response message with the PDU session identity at step S1005.
When the SMF accepts to establish the PDU session, the SMF sends a create PDU session accept message to the MMF at step S1006.
Then, the MMF forwards the received create PDU session accept message to the UE at step S1007.
However, if the SMF rejects to establish the PDU session, the SMF sends a create PDU session reject message to the MMF at step 1008.
Then, the MMF forwards the received create PDU session reject message to the UE at step S1009.
As described above, if the SMF rejects the request, the SMF does not request the allocation of the PDU session identity. In this method, the MMF does not need to know what type of SM message is forwarded to the SMF or UE.
However, this method may increase inter-MMF and SMF signaling because the PDU session identity allocation request/response message is generated whenever a new PDU session is created. Also when the PDU session is released, the PDU session identity deallocation request/response messages are exchanged between the MMF and the SMF.
Considering the number of message exchanges between the MMF and the SMF, it is proposed that the MMF allocates a PDU session identity when it receives a create PDU session request message.
Therefore, the MMF allocates the PDU session identity when it receives a create PDU session request message from UE. The MMF relays the SM message to the SMF having an allocated PDU session identity.
This solution assumes that only one MMF is present when UE is attached to a network. According to the current interim agreement, a single NG1 NAS connection is used when UE is attached via 3GPP access. There is no agreement about whether the same MMF is used when UE is attached simultaneously via 3GPP and non-3GPP accesses.
So it is proposed that if a different MMF is allocated when UE attached simultaneously via 3GPP and non-3GPP accesses, each entity (i.e., UE, MMF or SMF) stores a PDU session identity for each access network. If the same MMF is allocated, the PDU session identity may be stored without the distinction of access networks.
Therefore, if a different MMF is allocated when UE is attached simultaneously via 3GPP and non-3GPP accesses, each entity (i.e., UE, MMF or SMF) stores a PDU session identity for each access network. Otherwise, if the same MMF is allocated, the PDU session identity is stored without the distinction of access networks.
Session management and service continuity are arranged as follows based on the contents of the above description.
The NextGen core (NGC) supports dual stack UE by using separate the PDU sessions for IPv4 and IPv6.
The NGC does not support dual stack PDU session (PDU session type IPv4v6).
An SMF entity in the serving PLMN and an SMF entity in the HPLMN are involved.
At least UPF in the serving PLMN and at least UPF in the HPLMN are involved.
This means that the SMF in a visited PLMN (VPLMN) is not meant to understand some of the information exchanged between the UE and the network in NAS signaling but relays it transparently to the SMF in a home PLMN (HPLMN). The SMF in the HPLMN is responsible for checking whether via this NAS information transparently relayed by the SMF in VPLMN is compliant with the user subscription.
The SMF in the VPLMN is nevertheless assumed to understand some of the NAS information related with a PDU session for deployments with SM the PDU session control in the HPLMN.
The SMF in the VPLMN needs to handle and to check with regard to roaming agreements QoS requests from the SMF in HPLMN.
“CN-prepared PDU Session modification followed by notification to UE (SSC mode 3)” is only endorsed for IPv6 traffic.
Furthermore, an interaction is described in brief as follows based on the contents of the above description with respect to the MM and the SM.
At this moment, the MMF stores an association between the SMF ID and the PDU session identity. When the MMF receives SM message which accepts release of the existing the PDU session, the MMF deallocates the PDU session identity and removes an association between the SMF ID and the PDU session identity.
According to the conclusion of overall architecture, if different MMF is allocated when the UE attached simultaneously via 3GPP and non-3GPP accesses, each entity (e.g., UE, the MMF, the SMF) stores the PDU session identity per access network. Otherwise, if the same MMF is allocated, the PDU session identity is stored without distinction of access network.
This may correspond to the following interaction:
NG2 impacts of SM events:
a. At the set-up/modification/release of a PDU session: the SMF interacts with RAN via MMF for setup, modification and release of radio and NG3 resources for the PDU session.
b. At the set-up/modification of QoS for GBR flows or modification of QoS rules for non-GBR flows, the SMF interacts with the RAN via MMF to provide the QoS information.
The impacts of MM events are as follows:
a. At the transition from IDLE to CONNECTED: the SMF interacts with the RAN via an MMF for setting up of radio and NG3 resources for the PDU session.
b. During handover: the SMF interacts with the MMF at least to receive from the RAN the NG3 DL information.
c. When UE becomes IDLE, the MMF notifies the SMF(s) in order for the SMF(s) to modify the settings for DL data forwarding in the NGUP(s) for NG3.
d. When it is made aware by the NGUP that some DL data has arrived for the UE in IDLE mode (and the UE is not known to be in a power saving state), the SMF interacts with the MMF in order to trigger UE paging from the AN (depending on the type of the AN).
e. The SMF may need to interact with the MMF in order to be able to control the NGUP(s) based on the power saving state of the UE.
f. When the UE sends (non periodic) TAU request to the MMF, the MMF may need to notify the SMF(s) so that the SMF(s) may determine whether user plane function relocation is required or not (based on SSC mode and on the new user location).
An interworking (including mobility) scenario between core networks (e.g., an NG core and an EPC) to which the present invention may be applied is as follows.
It is assumed that on the radio side the upgraded E-UTRAN supports the legacy LTE-Uu interface.
UE capable of supporting the NG NAS via the NG1 (i.e., Reference point for the control plane between NextGen UE and NextGen Core) interface may be called an NG core (NGC)-capable UE.
It is assumed that in addition NGC UE is capable of supporting:
The UE will use EPC NAS or NG NAS depending on the core network by which it is served.
The UE will always use the NG NAS when connecting to the NG RAN. The UE may use the NG NAS when connecting to E-UTRAN.
In all the architectures for the various scenarios, it is assumed that the EPC and the NGC have access to a common subscriber database.
In this solution, all interworking scenarios assume single-CN registration at any point in time for the 3GPP RATs (i.e., similar to EPC).
Service continuity is provided for the various scenarios as described below.
In this solution, an NGx interface is introduced between the MME and NG core AMF in order to enable interworking between EPC and the NG core. NGx is an inter-CN interface PCF+PCRF is involved if policy and charging is controlled in a dynamic way.
A policy control function (PCF)+a policy and charging rules function (PCRF), a PGW control plane (PGW-C)+an SMF and UPF+PGW user plane (PGW-U) are dedicated for interworking between the NextGen system (NGS) and the EPS, which are optional and are based on UE and network capabilities. UEs that are not subject to EPS and NGS interworking may be served by entities not dedicated for interworking, i.e., either by the PGW/PCRF or the SMF/UPF/PCF.
Even though not shown in the
When connecting to the E-UTRAN, UE uses EPC NAS with the core network. In such a scenario, when connected to a non-evolved E-UTRAN, the UE authentication, mobility management and session management are performed by the MME towards the UE.
In order to support idle or connected mode mobility between EPC and NG Core, the UEs serving MME connects via a control plane NGx interface to CP functions in the NGC, and the UE's serving SGW connects via a user plane S5-U interface to user plane functions in the NGC and via a control plane S5-C interface to CP functions in the NGC. A user plane should always be anchored in NG CN for UE with NG RAN subscription. The GW selection may still be done by the MME with the current mechanisms, and will result in a GW in the 5G CN.
Interworking with NextGen in this solution is performed by:
Service continuity is provided between the E-UTRAN and the NG RAN options deployed by the operator via Interworking Function and the common anchoring of the user plane. Inter-RAN PDU forwarding may be supported.
How a PDU session ID is allocated when UE handovers from the EPC to the 5G core network is described below with reference to
1. The E-UTRAN determines to handover UE served over the E-UTRAN from the E-UTRAN (e.g., eNB) to the 5G RAN due to a radio condition.
2. If the E-UTRAN determines to handover the UE from the E-UTRAN to the 5G RAN, the E-UTRAN notifies the MME of such handover. That is, the E-UTRAN sends a handover required message to the MME.
In this case, the handover required message may include a target 5G RAN identity (ID) and a source to target transparent container.
The source to target transparent container may include information that needs to be transparently transferred by core network entities from a source RAN (i.e., the E-UTRAN) to a target RAN (i.e., the 5G RAN).
In this case, the MME may request EPS bearer context, including mapped SM context, from the PGW.
3. The MME may hand over the context of the corresponding UE, owned by the MME, to the AMF.
That is, the MME sends a relocation request message to the AMF (or the MMF or a common CP function).
In this case, the relocation request message may include the UE context. For example, the UE context may include an international mobile subscriber identity (IMSI), a mobile equipment (ME) identity, UE security context, an aggregate maximum bit-rate (AMBR), an S-GW address and/or EPS bearer context (e.g., a P-GW address, an access point name (APN) and an S-GW address).
Furthermore, the relocation request message may include a target 5G RAN ID and a source to target transparent container.
4. The AMF selects an SMF based on the UE context information (e.g., PDN connection information (or EPS bearer context) owned by the UE) received from the MME.
In this case, the P-GW address to which a PDN connection is connected may be used as the information necessary to select the SMF.
a. If the method of Option 2 is used to allocate a PDU session ID, the AMF may allocate a network slice ID (e.g., NSI identity) in addition to the PDU session ID. In this case, the PDU session may be identified by a combination of the NSI identity and the PDU session ID.
If multiple SMFs are present in a single network slice, a process of additionally allocating an ID (e.g., SMF identity) unique to each SMF within each network slice is performed. In this case, the PDU session may be identified by a combination of the NSI identity, the SMF identity and the PDU session ID.
b. If the method of Option 3 is used to allocate a PDU session ID, the AMF may directly allocate the PDU session ID and transfer it to the SMF at step 5. In this case, the PDU session may be identified by the PDU session ID.
If multiple PDU sessions are present in a single SMF, the SMF needs to be notified of a PDU session ID allocated to each PDN connection (i.e., PDU session).
5. The AMF sends a request for establishing a PDU session to the SMF selected at step 4. That is, the AMF sends a session creation (or modification) request message to the SMF.
In this case, the AMF may send a session creation (or modification) request message to the SMF for each PDN connection (i.e., PDU session).
In this case, the determined PDU session ID information is transferred to the SMF depending on each option at step 4. That is, if the method of Option 2 is used at step 4, a network slice ID (e.g., NSI identity)+the SMF ID information may be transferred to the SMF. Alternatively, if the method of Option 3 is used at step 4, the PDU session ID information may be transferred to the SMF.
6. The SMF determines a PDU session ID.
In this case, the SMF may determine the PDU session ID based on the information received from the AMF.
a. If the method of Option 1 is used to allocate a PDU session ID, the SMF allocates a PDU session ID within a preconfigured PDU session ID pool to the PDU session regardless of the information received from the AMF.
b. If the method of Option 2 is used to allocate a PDU session ID, the SMF allocates a (local) PDU session ID to the PDU session along with a network slice ID (e.g., NSI identity)+SMF ID information received from the AMF. That is, the SMF allocates the PDU session ID to the PDU session by combining the network slice ID+the SMF ID+the (local) PDU session ID.
c. If the method of Option 3 is used to allocate a PDU session ID, the SMF determines to allocate the PDU session ID to the PDU session using the PDU session ID received from the AMF without any change.
d. If the method of Option 4 is used to allocate a PDU session ID, the SMF includes its own globally unique ID value in the PDU session ID when allocating the PDU session ID, and allocates the PDU session ID to the PDU session.
Furthermore, the SMF also notifies the AMF of information about the PDU session ID allocated at step 6. That is, the SMF sends a session creation (or modification) response message to the AMF.
The AMF that has received the session creation (or modification) response message from the SMF stores the PDU session ID and association with the SMF, and stores information about how each PDN connection (i.e., PDU session) is mapped to which PDU session ID.
7. The AMF makes the 5G RAN prepare for handover of the UE by sending a handover request message to the 5G RAN.
8. After the 5G RAN prepares radio resources based on radio information received from the E-UTRAN, it notifies the AMF that it has been prepared for handover by sending a handover request acknowledgement message to the AMF.
9. The AMF notifies the MME that both the 5G RAN and the 5G core have finished the preparation of handover by sending a relocation response message to the MME.
10. The MME performs an operation for creating a forwarding tunnel for sending downlink packets generated during handover to the 5G core.
11-12. The MME sends a handover command to the E-UTRAN after all of handover preparation operations are completed. Furthermore, the E-UTRAN instructs the UE to handover to the 5G RAT, that is, a target access network, by sending the handover command to the UE.
13-14. When the UE successfully accesses the 5G RAT (i.e., when the 5G RAT receives a handover complete message from the UE), the 5G RAT notifies the AMF that the handover is successful completed by sending a handover notify message to the AMF.
15-16. The AMF notifies the SMF that the handover has been completed by sending a session creation (or modification) request message to the SMF+PGW-C. Furthermore, the SMF+PGW-C performs acknowledgement by sending a session creation (or modification) response message as a response to the session creation (or modification) request message.
From this moment, the SMF starts to send downlink traffic to the 5G RAN.
17. Thereafter, the MME/AMF on which the handover has been performed releases the forwarding tunnel.
18. After the handover is completed, the UE performs registration update (e.g., a tracking area update operation). In this process, the AMF sends information about which PDN connection has been mapped to which PDU session based on the information stored at step 6 and the allocated PDU session ID to the UE through a registration update accept message. In addition, the AMF may send additional information (e.g., information about a session and a service continuity mode) about the PDU session to the UE.
Referring to
In this case, if UE requests the establishment of a PDU session from a network due to a reason, such as the first access of the UE to a network, as in
Furthermore, the name of the create session request message is only an example, and another name may be used as a message to request the establishment of a PDU session.
When the SMF receives the create session request message, it determines a PDU session identity for a PDU session established for UE (S1602).
a. The SMF node may determine the PDU session identity for the PDU session for the UE by selecting the PDU session identity randomly or according to a predetermined rule within a PDU session ID pool configured for the SMF node.
b. Alternatively, the SMF may determine the PDU session identity for the PDU session for the UE by combining a network slice identity to which the SMF belongs and an identity for locally identifying a PDU session within the SMF.
In this case, the network slice identity may be allocated by the AMF, may be included in the create session request message at step S1601, and may be transmitted by the AMF.
If multiple SMFs are present in a network slice, the SMF may determine the PDU session identity for the PDU session for the UE by combining an SMF identity for identifying each SMF within a network slice, the network slice identity to which the SMF belongs, and the identity for locally identifying the PDU session within the SMF.
In this case, the network slice identity and the SMF identity of the SMF may be allocated by the AMF, may be included in the create session request message at step S1601, and may be transmitted by the AMF.
c. Alternatively, the SMF may receive the PDU session identity for the PDU session for the UE through the create session request message at step S1601 from the AMF. In this case, the SMF may determine a PDU session ID to be used in the PDU session using the PDU session ID received from the AMF without any change.
More specifically, when the AMF receives the create session request message from the UE, it may allocate a PDU session identity. Furthermore, the AMF may transfer the create session request message, including the allocated PDU session identity, to the SMF at step S1601. In this case, the AMF may create association between the ID (i.e., SMF ID) of the corresponding SMF and the PDU session identity.
d. Alternatively, the SMF may determine the PDU session identity for the PDU session for the UE by combining a globally unique ID value allocated thereto and an identity for locally identifying a PDU session within the SMF.
The SMF sends a create session response message, including the PDU session identity determined at step S1602, to the AMF in response to the create session request message (S1603).
Furthermore, the AMF that has received the create session response message from the SMF stores association between the PDU session ID and the SMF, and stores information about how each PDN connection (i.e., PDU session) is mapped to which PDU session ID.
If the AMF receives a create session reject message from the SMF other than the create session response message or receives indication having the same meaning from the SMF, it is necessary to deallocate the PDU session identity allocated by the AMF.
More specifically, when the AMF receives the create session reject message from the SMF or receives indication having the same meaning from the SMF (i.e., when the creation/establishment of the PDU session are rejected), the AMF deallocates the allocated PDU session identity. In this case, the AMF may remove association between the ID (i.e., SMF ID) of the corresponding SMF and the PDU session identity.
In this case, the name of the create session response message is only an example, and another name may be used as a message including the PDU session identity, that is, a response to the create session request message.
Furthermore, the name of the create session reject message is only an example, and another name may be used as a message for rejecting the creation of a session, that is, a response to the create session request message.
Device to which the Present Invention May be Applied
Referring to
The network node 1710 includes a processor 1711, memory 1712, and a communication module 1713. The processor 1711 implements the functions, processes and/or methods proposed in
The network node 1710 may be an SMF, an AMF, a BS, an MME, an HSS, an SGW or a PGW, for example. More specifically, if the network node 1710 is a BS, the communication module 1713 may include a radio frequency (RF) unit for transmitting/receiving a radio signal.
The UE 1720 (e.g., terminal) includes a processor 1721, memory 1722, and a communication module (or RF unit) 1723. The processor 1721 implements the functions, processes and/or methods proposed in
The memories 1712 and 1722 may be present inside or outside the processors 1711 and 1721 and may be connected to the processors 1711 and 1721, respectively, by various well-known means. Furthermore, the network node 1710 (in the case of a BS) and/or the UE 1720 may have a single antenna or multiple antennas.
Particularly,
Referring to
The processor 1810 implements the functions, processes and/or methods proposed in
The processor 1810 is connected to the processor 1810 and stores information related to the operation of the processor 1810. The memory 1830 may be located inside or outside the processor 1810 and may be connected to the processor 1810 by various well-known means.
user inputs, for example, instruction information such as a phone number by pressing (touching) a button of the keypad 1820 or by voice activation using the microphone 1850. The processor 1810 performs an appropriate function, such as the reception of such instruction information and making a phone call to a phone number. Operational data may be extracted from the SIM card 1825 or the memory 1830. Furthermore, for user recognition and convenience, the processor 1810 may display instruction information or driving information on the display 1815.
The RF module 1835 is connected to the processor 1810 and transmits and/or receives an RF signal. In order to start communication, the processor 1810 transfers, for example, instruction information to the RF module 1835 and transmits a radio signal forming voice communication data. The RF module 1835 is configured to include a receiver and a transmitter for receiving or sending a radio signal. The antenna 1840 performs the function of transmitting or receiving a radio signal. When receiving a radio signal, the RF module 1835 may transfer the signal so that it is processed by the processor 1810 and may convert the signal having a baseband. The processed signal may be converted into audible or readable information and output through the speaker 1845.
In the aforementioned embodiments, the elements and characteristics of the present invention are combined in a predetermined form. Unless phrases explicitly represent, it should be considered that each element or characteristic is selective. Each element or characteristic may be implemented in a form in which the element is not combined with other elements or characteristics. Furthermore, an embodiment of the present invention may be configured by combining some configurations and/or characteristics. The sequence of the operations described in the embodiments of the present invention may be changed. Some configurations or characteristics of any embodiment may be included in another embodiment or may be replaced with a configuration or a characteristic corresponding to another embodiment. It will become apparent that claims that are not in an explicit cited relation in the claims may configure an embodiment by combination and may be included in new claim by amendment after filing.
The embodiment of the present invention may be implemented by various means, for example, hardware, firmware, software, or combinations thereof. When an embodiment of the present invention is implemented by hardware, it may be implemented by at least one application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), a processor, a controller, a microcontroller, and a microprocessor.
When an embodiment of the present invention is implemented by firmware or software, it may be implemented in the form of a module, procedure, and function that perform the aforementioned function or operation. A software code may be stored in the memory to be driven by the processor. The memory may be located inside or outside the processor and may transmit or receive data to or from the processor by already known various means.
It will become apparent to a person having ordinary skill in the art that the present invention may be embodied in different specific forms without departing from the essential features of the present invention. Therefore, it should be considered that the detailed description is not to limit the present invention but to illustrate it. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.
An embodiment of the present invention mainly describes an example applied to a 3GPP LTE/LTE-A system or 5G system, but may be applied to various wireless communication systems other than the 3GPP LTE/LTE-A system and 5G system.
Kim, Hyunsook, Youn, Myungjune
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